Heat exchange apparatus

ABSTRACT

Heat exchange apparatus comprises first and second heat exchange units 2, 4 with spiral pathways, each unit having a central volute which contains a respective impeller 18, 24. The pathways of each unit are separated by flexible metallic strips 14/15/16. The impellers are driven by a common motor 26 therebetween. The apparatus is intended for use in heat exchange between air streams, for example between an air stream extracted from a building and an air stream extracted from outside. Mixing of the air streams is prevented.

This invention relates to heat exchange apparatus for exchanging heatbetween fluids. The heat exchange apparatus may, for example, findapplication as part of an air conditioning unit or a heat pump. Theinvention relates in particular to a compact heat exchange apparatussuitable for application as a room or car air conditioner/heater.

According to the present invention there is provided heat exchangeapparatus, comprising a first heat exchange unit and a second heatexchange unit, each heat exchange unit having a fluid impeller and aheat conductive wall about the impeller, wherein each said unit has afirst flow pathway, about the impeller, internally of the wall, and asecond flow pathway, externally of the wall; the first and second unitsbeing so connected that the first flow pathway of the first unitcommunicates, via the impeller of the first unit, with the second flowpathway of the second unit; and the first flow pathway of the secondunit communicates, via the impeller of the second unit, with the secondflow pathway of the first unit.

Preferably the wall of each heat exchange unit is of spiral form therebyenclosing a volute within which the impeller is located. Preferably, thefirst pathway of each unit continues beyond the volute in a spiralconformation.

Suitably a second heat conductive wall of spiral shape is provided ineach heat exchange unit, serving as the outer wall of the second flowpathway. Each heat exchange unit may thus comprise two flow pathways ofspiral conformation, interleaved with each other, and isolated from eachother by means of two heat conductive walls.

Fluid flow in the second pathway of each heat exchange unit ispreferably in the spiral direction, though could, in certainembodiments, be in the axial direction.

The second flow pathway of each heat exchange unit may communicate witha transfer port located substantially at the innermost region of thepathway, the transfer port permitting fluid to enter or leave thepathway by flow in a direction which is transverse to the flow, in aspiral direction, within the pathway.

Preferably, in use, the fluid is moved in one sense along one pathwayand in the opposite sense along an adjacent pathway, in each unit. Eachunit may have two fluid pathways as described, or may have further suchfluid pathways, each fluid pathway being separated from each adjacentpathway by a heat conductive wall.

Preferably, the heat conductive wall(s) is/are constituted by flexiblestrip(s), preferably of a metallic material. Preferably the metallicmaterial is thin, suitably about 0.1-0.5 mm, so that its heat capacityis low, whereby the thermal lag of the heat exchange unit is low.

In a heat exchange apparatus as previously described, each said heatexchange unit comprises a fluid impeller, for example a centrifugal fan,located in its eye, suitably a volute. The fluid impellers arepreferably driven by a common motor, suitably located between theimpellers. In this way, a heat exchange unit in accordance with theinvention may be compact, yet provide efficient heat transfer.

In a particularly compact heat exchange apparatus the first and secondunits are located together substantially in face-to-face contact, thefirst and second units defining respective hollows, which oppose eachother but with a lateral offset from each other, wherein the units havepartitioning between them, the arrangement being such that thecommunication between the second flow pathway of the first unit and thefirst flow pathway of the second unit is via a transfer port in thepartitioning at the position at which the second hollow extendslaterally beyond the first hollow, and via the impeller of the secondunit; and the communication between the second flow pathway of thesecond unit and the first flow pathway of the first unit is via atransfer port in the partitioning at the position at which the firsthollow extends laterally beyond the second hollow, and via the impellerof the first unit. Preferably, the second heat unit is arranged upsidedown relative to the first unit and the said hollows are axialcontinuations of respective volutes of the units, wherein each transferport is aligned with a region of the volute of the other unit.

Heat exchange apparatus in accordance with the present invention iscompact and efficient, and is particularly well suited for the exchangeof heat between gaseous media, for example, air/air. It may beespecially useful as an air conditioner/heater for use in a car orbuilding, extracting air from the interior and bringing in air from theexterior; in winter extracting heat from the outgoing interior air andtransferring it to the incoming exterior air, and in summer extractingheat from the incoming exterior air and transferring it to the outgoinginterior air. In so doing, moreover, condensation problems are reduced,the interior air generally being moister then the exterior air.Efficient car or household heat exchange apparatus, comprising two heatexchange units, as previously described, may be a cube of size about 30cm.

One embodiment of heat exchange apparatus in accordance with the presentinvention is through-wall heat exchange apparatus, exchanging heatbetween a car or room of a house, and the outside. In this context itmay be desirable to employ an auxiliary heating device, conveniently anelectric heating element, to increase the amount of heat which the unitcan give to the incoming air. It may be desirable to provide an electricheating element in a distinct unit which is securable to the heatexchange apparatus, over the "inside outlet" thereof. For example, thismight be useful if such a heat exchange apparatus were used to provideventilation for a bathroom, heat being extracted from the exhaust airand steam and provided by the heating element.

Preferably there is provided, for use with heat exchange apparatus inaccordance with the present invention, singly or in combination, one ormore modules securable to the apparatus, for example a heater module asdescribed above, a cooling module, a humidifying or dehumidifyingmodule, an electrostatic filter module or a perfuming/room fresheningmodule. Such modules may conveniently be securable over the "interioroutlet" of the unit, for example replacing the standard fascia of theunit.

Heat exchange apparatus for use in a household context can be a mainapparatus serving a number of rooms via ducting. In general the modulesdescribed above may be incorporated in the ducting or at the "interioroutlets" of such a system. Heater or cooling modules, when provided, arepreferably located at the "interior outlets".

In accordance with another aspect of the invention, therefore, there isprovided heat exchange apparatus or a heat exchange unit, for heatexchange between air streams, in association with one or more modulessecurable thereto, to provide a qualitative change of the air in atleast one of the air streams.

A heat exchange unit in accordance with the invention may findapplication in other areas, for example, as a high temperature heatexchanger, or as a heat pump.

In accordance with a further independent aspect of the invention thereis provided a method of making a heat exchange unit for transferringheat from one flow pathway to another flow pathway the pathways being ofspiral conformation, interleaved with each other, and separated fromeach other by a plurality of spaced-apart strips of a flexible material(preferably metallic), which method comprises providing a pair ofspaced-apart side plates for the unit, each side plate having aplurality of spaced-apart spiral grooves, aligned with and facingcorresponding grooves of the other side plate, each pair of alignedgrooves serving as guides for the lateral edges of a strip; and feedingthe strips into the grooves, lengthwise, to the extent permitted by thegrooves.

The invention will now be described, by way of example, with referenceto the accompanying drawings, in which:

FIG. 1 is an exploded schematic view of heat exchange apparatus inaccordance with the invention;

FIGS. 2a, 2b and 2c show respectively, in schematic form, a centralportion and left and right end portions of heat exchange apparatus;

FIG. 3 is a cross-sectional view, of heat exchange apparatus;

FIG. 4 demonstrates a step in a method of constructing heat exchangeapparatus in accordance with the invention;

FIG. 5 shows in schematic cross-sectional view a further embodiment ofheat exchange apparatus in accordance with the invention;

FIG. 6 shows, in schematic cross-sectional view, a further embodiment;and

FIGS. 7 and 8 show a further embodiment respectively in schematiclongitudinal and transverse cross-sections, FIG. 7 being a view alongsection A-A1 shown in FIG. 8.

FIGS. 1, 2 and 3 show very similar embodiments and will be describedtogether. Throughout the drawings, like parts of different embodimentsare referred to using like reference numerals.

With reference to FIGS. 1, 2 and 3, the heat exchange apparatuscomprises a first heat exchange unit 2, and a second heat exchange unit4, units 2 and 4 being arranged side by side with a space between them.

The first heat exchange unit 2 comprises two interleaved spiral flowpathways 6, 8. Each spiral pathway is bounded by parallel side walls 10,12 (FIG. 3), suitably of a plastics material, and by a pair of flexiblealuminium strips 14/15 and 15/16, set between the side walls 10, 12. Thecentral strip 15 acts as a barrier separating the flow pathways 6 and 8,as does the strip 14 in its innermost region. In the FIG. 2 embodimentonly two strips, 14, 15 are provided. As will be seen in FIG. 1, eachspiral pathway extends for between one and two revolutions. The innerpathway 8 commences at an inner volute 17 within which a conventionalcentrifugal impeller 18 is located, the side wall 12 adjacent theimpeller 18 having a circular opening 19 slightly larger than theimpeller cross-section. The position of the opening 19 is shown indotted line in FIG. 1, in which the side wall 12 is not shown. Thevolute 17 within the spirals is considerably larger than the opening 19.Mounted on the outside of the side wall 12 is an eye plate 20 (FIG. 3)having a circular aperture corresponding in size with and aligned withthe interior cross-section of the impeller, and whose rim 21 is formedwith a taper to guide air into the interior of the impeller.

The outer flow pathway 6 terminates at an end closure or blind wall 22,the aluminium strips 14, 15 coming together at this point. A nosing (notshown) may be provided, if desired, into which the ends of the stripslocate. Just before the blind wall is reached, there is a transverseslot-like transfer port 23, formed in the side wall 12, providing anoutlet from this flow pathway.

Arranged alongside the unit 2, but spaced apart from it, is the secondheat exchange unit 4 of identical form but arranged upside down relativeto the unit 2. The respective impellers 18, 24 of the first and secondheat exchange units are driven by a common shaded pole motor 26 locatedbetween them.

It should be noted that the motor is within an enclosure 27 defined byopposed side walls 12, 28 of the first and second heat exchange units,and cross walls 30 therebetween. Within the enclosure, there is astepped internal partition 32 extending between one side wall 12 and theother side wall 28, such that the opening 19 into the volute of eachheat exchange unit communicates with the slot-like transfer port of theother heat exchange unit.

In use, with the motor 26 rotating both impellers 18, 24, and with theapparatus arranged, in this example, in an external wall of a building,stale interior air is drawn into the outer flow pathway 6 of heatexchange unit 2, and around the pathway to the transfer port 23, whereit leaves the unit, and passes into the heat exchange unit 4 via theopening 19 into the eye thereof. From there, it passes, via the impeller24, to the volute, at the start of the inner spiral pathway of heatexchange unit 4, along that pathway and then to the outside atmosphere.In so doing, it gives up a substantial amount of heat to the incomingair, which is drawn into the outer pathway of heat exchange unit 4,leaving this apparatus by the slot-like opening 32, passing to thevolute at the start of the inner spiral pathway of heat exchange unit 2along that pathway, and into the building.

In the embodiment of FIGS. 1 to 3, there is a pair of flow pathways ineach heat exchange unit, with the apparatus being arranged so that airpasses through these in opposite directions. In other embodiments thereare two pairs of such adjacent pathways, with the apparatus beingarranged so that air passes through adjacent pathways in oppositedirections, both pathways for incoming air terminating in blind walls,and being formed with slot-like outlets adjacent the blind walls. Fromthere, air passes into the volute of the second heat exchange unit, asdescribed with reference to FIGS. 1 to 3, but the volute communicateswith two spiral pathways which convey the air to the exterior. It willmoreover be appreciated that the flow pathways may be narrower, andextend through more revolutions, that is shown by the schematicdrawings, which are presented herein for the purpose of clarity. Anexample of a "tightly wound" spiral heat exchanger is shown inGB-A-2140549. Similarly "tightly wound" spiral configurations could beemployed in the present invention.

Further pathways may be provided; for example it is quite possible tohave six or more pathways in a heat exchange unit.

The manufacture of a heat exchange unit 2, 4 in accordance with theinvention may be facilitated by forming the side walls 10, 12 inmanufacture with appropriately shaped guides or grooves to receive thin,flexible aluminium strips (FIG. 4), suitably of about 0.25 mm thickness.For example, the side walls may be pressed or moulded into theappropriate shape. Grooves to receive the steel strips are shown as 40.Side walls 10, 12 of a heat exchange unit are in alignment with eachother, as shown in FIG. 4, and the aluminium strips are fed into placeby lengthwise movement. The strips follow the spiral grooves until theycan travel no further, having reached the end of the grooves. In theembodiment shown, adjacent grooves meet at the innermost part of thespiral, so that when adjacent strips have been pushed into place, theyabut with each other at the end of one of the pathways. Alternatively, anosing may be provided, into which they locate.

In FIG. 5 there is shown a more compact heat exchange apparatus in whichthe spiral pathways, not shown in detail but generally indicated bycross-hatching, of each heat exchange unit 2, 4, extend to the centreplane of the apparatus. The motor 26 is located in a central spaceconstituted by hollows 40, 42 defined in the units 2, 4 respectively.The hollows are aligned with--effectively axial extensions of--thevolutes V of the units. The two hollows face each other but arelaterally displaced from each other to a small extent and do notcommunicate with one another, a partition 44 being provided, around themotor 26. The partition 44 extends further out so that the spiralpathways of unit 2 are not directly in communication with spiralpathways of unit 4. However, the partition has two apertures 22, 32, atthe position at which the hollows 40, 42 are displaced beyond eachother. The apertures 22, 32 constitute the transverse transfer portsfrom spiral pathways of units 2, 4. It will thus be appreciated, and isseen in FIG. 5, that exhaust air into unit 2 passes through aperture 22on leaving its spiral flow path and then passes into the core of thecentrifugal fan of the unit 4, thence to the outflow spiral flow path ofunit 4; and that the intake air into unit 4 passes through aperture 32on leaving its spiral flow path and thence into the core of thecentrifugal fan of the unit 2, thence to the outflow spiral flow path ofthe unit 2.

The embodiment of FIG. 5 is compact because of the elimination of thespacing between the heat change units as provided in the embodiment ofFIG. 1 to 3.

FIG. 6 shows schematically a simple embodiment in which the innerpathway 8 is effectively entirely constituted by a volute of acentrifugal impeller 18, and an outer pathway 6 is for the axial passage(into the place of the paper) of, for example, air or water.

FIGS. 7 and 8 show an embodiment of heat exchange apparatus similar tothe embodiment of FIG. 5, and in greater detail, showing the heatconductive barriers. It will be clearly seen from FIG. 7 that thehollows 40, 42 are axial extensions of the volutes V. FIG. 8 shows theunit 4 (whose spiral walls are shown in dotted line) arranged upsidedown relative to unit 2, whose spiral walls are shown in solid line,with the transfer port 32 of unit 4 aligned with a region of the voluteof unit 2, and the transfer port 22 of unit 2 aligned with a region ofthe volute of unit 4. It will moreover be observed in FIG. 7 that eachunit also has a outer-facing hollow 50, an axial extension of thevolute, at its end which is remote from the other unit. The hollow 50may receive electrical control apparatus, for example switchgear,thermostat, etc.

In FIG. 8 the region of each inner pathway between the dotted lines X(for unit 2), and Y (for unit 4) is a ramped region in which the innerpathway widens axially to compensate for the radial narrowing of thepathway as it leaves the volute, and prevent turbulence/stalling of theair. In FIG. 7, the ramp is schematically indicated by dotted lines 60as is the nosing 62 at the end of the inner spiral pathway.

I claim:
 1. Heat exchange apparatus, comprising a first heat exchangeunit and a second heat exchange unit, each heat exchange unit having afluid impeller and a heat conductive wall surrounding the impeller,wherein each said unit has a first flow pathway, surrounding theimpeller, internally of the wall, and a second flow pathway, externallyof the wall; the first and second units being so connected that thefirst flow pathway of the first unit communicates, via the impeller ofthe first unit, with the second flow pathway of the second unit; and thefirst flow pathway of the second unit communicates, via the impeller ofthe second unit, with the second flow pathway of the first unit.
 2. Heatexchange apparatus as claimed in claim 1, wherein the wall of each unitis of spiral form thereby enclosing a volute within which the impellerof the respective unit is located.
 3. Heat exchange apparatus as claimedin claim 2, wherein the first flow pathway of each unit continues beyondthe volute in a spiral conformation.
 4. Heat exchange apparatus asclaimed in claim 2, wherein each unit comprises a second heat conductivewall of spiral form which serves as the outer wall of the second flowpathway of the respective unit.
 5. Heat exchange apparatus as claimed inclaim 1, wherein the first and second units are located togethersubstantially in face-to-face contact, the first and second unitsdefining respective hollows, which oppose each other but with a lateraloffset from each other, Wherein the units have partitioning betweenthem, the arrangement being such that the communication between thesecond flow pathway of the first unit and the first flow pathway of thesecond unit is via a transfer port in the partitioning at the positionat which the second hollow extends laterally beyond the first hollow,and via the impeller of the second unit; and the communication betweenthe second flow pathway of the second unit and the first flow pathway ofthe first unit is via a transfer port in the partitioning at theposition at which the first hollow extends laterally beyond the secondhollow, and via the impeller of the first unit.
 6. Heat exchangeapparatus according to claim 5, wherein the second unit is arrangedupside down relative to the first unit and the said hollows are axialcontinuations of respective volutes of the units, wherein each transferport is aligned with a region of the volute of the other unit.
 7. Heatexchange apparatus as claimed in claim 1, wherein the impellers aredriven by a common motor.
 8. Heat exchange apparatus as claimed in claim7, wherein the motor is located between the impellers.
 9. Heat exchangeapparatus as claimed in claim 1, adapted to exchange heat between airstreams passing along respective flow pathways.
 10. Heat exchangeapparatus as claimed in claim 1, in situ in the external wall of thebuilding, to exchange heat between exhaust air drawn from the interiorof the building and intake air drawn from outside.